The Thomas Edison model of centralized power generation is outdated. Personal and distributed generation of energy, not just electricity, will replace centralized generation. Co-generation of utilities beyond just electricity to include heat and chill replaces centralized generation of power.
Co-generation allows local and distributed generation of multiple utilities, offering many advantages that centralized generation cannot. First, waste heat from electricity generation is captured. Large and centralized power plant not only wastes the residual heat, it also uses a large amount of water to dissipate that heat for the purpose of condensing steam from as steam turbine.
Distributed co-generation does not require the use of an expensive and often unreliable electric grid, thereby reducing cost and eliminating transmission loss. Distributed co-generation also has the advantage of using energy source that is local, for example by concentrated solar energy. Part of the reason why power utilities are centralized is to avoid the highly undesirable heat, sound, and air pollution of power plants. The location of the power plant must therefore be removed from population centers, thereby requiring a grid to deliver the power generated to where people live.
In places where sunshine is not abundant, natural gas could be used for distributed co-generation of electricity and heat. Such co-generation methods are becoming popular in Europe and Japan. Fossil fuel is burned to generate steam for a steam turbine. The waste heat from combustion, and from spent steam, is then used for space and water heating.
Schemes were proposed for tri-generation of heat, chill, and electricity. The generation of chill is from absorption chilling, such as using the waste heat of combustion and heat engine to evaporate a refrigerant from an absorbent. The refrigerant is subsequently condensed. Chill is produced when the refrigerant is evaporated under reduced pressure.
Thermodynamic cycles are used for many purposes. Refrigeration uses a reversed Rankine cycle in which a liquefied refrigerant is evaporated to create chill. Heat engine uses a Rankine cycle in which an evaporating working fluid is superheated under pressure to generate motion in a heat engine. Latent heat of gas and liquid and heat of condensation can be collected for heating up water. These three purposes can be combined in single cycle.
One way to refrigerate is by using carbon dioxide as refrigerant or working fluid. Carbon dioxide has gained popularity as a refrigerant because it has much less global warming potential than many of the refrigerants used today. Also, carbon dioxide provides a broader range of temperature for pumping heat. It can be used for heating water to boiling. It can also refrigerate at a much lower temperature without freezing.
Another example of a working fluid is water. Steam engines are Rankine cycle heat engines. Water is evaporated as steam. Steam is superheated to a high temperature and pressure to drive a piston. Heat energy is converted into work by the superheated steam pushing against the piston. The exhaust steam must be cooled to condense back into water. Condensed water is heated in an enclosed boiler to repeat the cycle.
Yet another working fluid is ammonia. The boiling point of ammonia at atmospheric pressure is in between the boiling points of water and carbon dioxide. Pressure requirements for liquefaction of ammonia are less than that required for carbon dioxide. The range of operating temperature for the heat pump based on ammonia is less than that for carbon dioxide, but more than that for water.